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Wrist joint
The wrist joint is the complex articulations of distal radioulnar, radiocarpal, midcarpal and carpometacarpal joints. * Distal (inferior) radioulnar: pivot joint with radius rotating around distal ulna. Distal ulna articulates with radius through an articular disc. * Radiocarpal: Ellipsoid joint created by the convex proximal carpal row (scaphoid, lunate, triquetrum) articulating with the concave surface of distal radius * Pisotriquetral: Gliding joint created by pisiform & triquetrum; discretely separate from radiocarpal joint in 10-25% * Midcarpal: between proximal & distal carpal rows Distal carpal row: * Carpometacarpal ** First CMC (thumb base): Saddle joint between trapezium and 1st MC ** Intermetacarpals 2nd-5th: Gliding joints between trapezium, trapezoid, capitate, hamate (distal row) and the 2nd to 5th MC. Wrist Motion * Tendon contribution to motion ** Flexion: FCU, FCR, PL, APL (FDS & FDP may assist when fingers are in full extension) ** Extension: ECRL, ERCB, ECU (ED & EPL may assist when fingers in clenched fist) ** Radial deviation (wrist abduction): APL, EPB with contribution by FCR, ECRL, ERCB, EPL ** Ulnar deviation (wrist adduction): FCU, ECU ** Pronation: PQ, PT ** Supination: Supinator, biceps brachii Nerves supply: three major nerves serve wrist region with articular nerves * Median - anterior interosseous * Ulnar - dorsal and deep branches * Radial - posterior interosseous Blood supply: supplied by three major arteries * Radial: Terminal branch of brachial artery * Ulnar: Terminal branch of brachial artery * Common interosseous: Branch of ulnar artery ** Branches into anterior & posterior interosseous arteries * Vessels create three major volar arches & one major dorsal arch and these supply articular arteries * Scaphoid has special supply from the recurrent branch from its distal pole from the radial artery. Capsule * Fibrous capsule encloses the joint * Attached proximally to the distal ends of the radius and ulna and distally to the proximal row of carpal bones Ligaments: extrinsic (connect radius, ulna to carpals or carpals to MC) or intrinsic (interconnect carpals) * Palmar radiocarpal: runs transversely from the lower end of the radius to the lunate * Dorsal radiocarpal * Ulnocarpal (ulnar collateral): Ulnolunate, ulnotriquetral; ulnocapitate * Intercarpal ligaments * Proximal interosseous, e.g. scapholunate * Distal interosseous * Distal radioulnar: Dorsal radioulnar, volar (palmar) radioulnar, articular disc (TFC) Muscles & Tendons * Muscles acting on the wrist joint or tendons crossing the wrist joints * Deep flexors ** Flexor digitorum profundus: ** Flexor pollicis longus ** Pronator quadratus * Superficial flexors ** Flexor carpi radialis: Origin medial epicondyle, insertion 2nd MC base with slip to 3rd MC ** Palmaris longus: Origin medial epicondyle, insertion superficial flexor retinaculum & palmar aponeurosis ** Flexor carpi ulnaris: Origin (humeral head) medial epicondyle & (ulnar head) medial olecranon/proximal ulna, insertion pisiform & flexor retinaculum ** Flexor digitorum superficialis: Origin (humeroulnar head) medial epicondyle & coronoid process of ulna & (radial head) anterior radius, insertion index through little finger middle phalangeal bases * Deep extensors ** Abductor pollicis longus ** Extensor pollicis brevis ** Extensor pollicis longus ** Extensor indicis * Superficial extensors ** Brachioradialis ** Extensor carpi radialis longus ** Extensor carpi radialis brevis ** Extensor digitorum ** Extensor digiti minimi ** Extensor carpi ulnaris * Thenar ** Abductor pollicis brevis ** Opponens pollicis ** Flexor pollicis brevis ** Adductor pollicis * Hypothenar ** Palmaris brevis ** Adductor digiti minimi ** Flexor digiti minimi brevis ** Opponens digiti minimi Retinacula * Flexor retinaculum ** Superficial (volar carpal ligament or ligamentum carpi palmare): Attached to styloid processes of ulna & radius; merges with deep component distally ** Deep (transverse carpal ligament or ligamentum flexorum): Attached to pisiform & hook of hamate medially, scaphoid & trapezium laterally * Extensor retinaculum ** Attaches to ulnar styloid process, triquetrum & pisiform medially, crosses obliquely to attach Lister tubercle & radial styloid process laterally *** Sends septae to radius creating compartments for extensor tendons ** Compartment contents: 1) APL, EPB; 2) ECRL, ECRB; 3) EPL; 4) ED, EI; 5) EDM; 6) ECU Anatomic Spaces * Anatomic snuffbox ** Margins: Distal radius (proximal margin), EPL (dorsal margin), APL & EPB (volar margin) convergence of APL/EPB just distal to 1st CMC (distal margin); snuffbox base formed by radial styloid, scaphoid, trapezium & 1st CMC ** Contents: Cephalic vein, radial nerve, (superficial branch), radial artery * Carpal tunnel ** Margins: Carpals (dorsal margin), flexor retinaculum (volar margin); pisiform & hook of the hamate (medial margin), scaphoid & trapezium (lateral margin), radiocarpal joint (proximal margin) & MC base (distal margin) ** Contents: FDS, FDP, FPL, median nerve * Guyon canal ** Margins: Superficial flexor retinaculum anteriorly, pisiform & FCU medially, deep flexor retinaculum laterally and posteriorly ** Contents: Ulnar artery & vein, ulnar nerve Variant anatomy Ulnar variance refers to the relative positioning of the ulnar and radial articular surfaces at the level of the radiolunate articulation. * neutral: same level * positive: ulna is distal to the radius * negative: ulna is proximal to the radius * Ossicles ** L: lunula ** O: os styloideum (carpal boss) ** T: (os) triangulare ** T: (os) trapezium secondarium ** E: (os) epilunate ** O: os hamuli proprium